The present invention relates to irrigation equipment, and more particularly, to rotor-type sprinklers that spray water over an adjustable arc.
Rotor-type sprinklers are widely used for watering lawns, golf courses, athletic fields and other landscaping. Typically such a sprinkler includes a cylindrical outer housing with a central riser that extends upwardly when the water is turned ON and retracts when the water is turned OFF. A head at the upper end of the riser includes a nozzle that directs a stream of water over the adjacent area. The head is rotated about a vertical axis by an internal turbine and gear drive through an predetermined arc whose ends limits are usually manually adjustable with a special tool. See for example, U.S. Pat. No. 3,107,056 granted Oct. 15, 1963 to Edwin J. Hunter and U.S. Pat. No. 4,568,024 granted Feb. 4, 1986 to Edwin J. Hunter.
Adjustable arc pop-up sprinklers typically have a reversing mechanism associated with the gear drive for the head. The direction of the water stream from the nozzle thus oscillates between pre-set end limits. These ends limits are usually trip points. For the sake of simplicity usually one end limit is fixed and the other end limit is moved along a circumferential ring or bull gear. Thus sector areas for watering can be pre-programmed such as forty-five degrees, seventy degrees, one hundred and eighty degrees, two hundred and seventy degrees, etc.
Adjustable arc sprinklers, like all sprinklers, are subject to vandalism. Frequently vandals will twist a riser of an oscillating pop-up sprinkler beyond its pre-set arc limits. Other times vandals will hold the riser against normal rotation by the internal drive. An adjustable pop-up sprinkler must therefore be constructed so it will not be permanently damaged if its riser is manually twisted or held against normal rotation, thereby forcing the head outside its pre-set arc limits. In addition, it is desirable to provide the adjustable arc sprinkler with the ability to automatically return its rotating head back to oscillation within the previously established end limits, otherwise an area that is not supposed to be watered receives water and visa versa.
U.S. Pat. Nos. 4,625,914 and 4,901,924 each disclose a sprinkler with a so-called "memory arc" mechanism that causes the head of the sprinkler to return to oscillation within preset arc limits after being twisted outside these limits by a vandal. However, in each case the memory arc mechanism is an integral part of the reversing mechanism for the head. If the memory arc mechanism fails even though a vandal has not forced the riser, the reversing mechanism can fail, such that the water stream does not move back and forth in the desired sector. In addition, after a vandal has twisted the riser so that its head is rotated outside the preset arc limits it can take as much as thirty seconds or more before the head of the sprinkler is returned to a position within its original arc limits. The amount of time varies depending upon the size of the pre-set arc, how far the riser has been twisted and the direction that the riser has been twisted. During this time, the full water stream is projected onto areas that are not supposed to receive water, such as walkways, roadways and the like, which can create safety hazards.